Devices are presently available for automatically analyzing electrocardiogram (ECG) signals to determine whether to treat a patient with a defibrillator. See, for example, U.S. Pat. No. 4,919,144, entitled "Defibrillator ECG Interpreter," which is hereby incorporated by reference. Such a devices use monitoring electrodes connected to a patient to collect ECG signals from the patient. The device then analyzes the collected ECG signals. If the device, by its analysis, determines that the patient should be treated, the device either defibrillates the patient or it advises an operator to trigger the device to defibrillate the patient. Defibrillation is accomplished by delivering an electrical charge to the patients through defibrillation electrodes connected to the patient. (In some cases, a single set of electrodes serves as both the monitoring electrodes and the defibrillation electrodes.)
Such devices use a single microprocessor executing an ECG analysis program to determine whether to treat the patient. While such devices commonly execute the analysis program multiple times in order to avoid treating the patient in response to spurious, false-positive ECG signals, failure of the single processor can cause these devices to erroneously determine that the patient should be treated and proceed to treat the patient erroneously. Failure of the single processor can also cause the devices to erroneously omit treatment of the patient.